The Collaborative International Dictionary of English v.0.48:

hot dog \hot" dog"\ (h[o^]t" d[add]g"), exclamation
   An expression of delight.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

hot dog \hot" dog`\ (h[o^]t" d[add]g`), n.
   1. A frankfurter.
      [PJC]

   2. A sandwich consisting of a hot dog inserted in a partly
      split elongated roll, usually garnished with mustard, and
      sometimes also with relish, sauerkraut, or a pickle. A hot
      dog garnished with a chili mix is called a chili dog.
      [PJC]

   3. A person who performs a complex and difficult athletic
      maneuver, usually to show off his/her skill.
      [PJC]

WordNet (r) 3.0 (2006):

hot dog
    n 1: someone who performs dangerous stunts to attract attention
         to himself [syn: hotdog, hot dog]
    2: a frankfurter served hot on a bun [syn: hotdog, hot dog,
       red hot]
    3: a smooth-textured sausage of minced beef or pork usually
       smoked; often served on a bread roll [syn: frank,
       frankfurter, hotdog, hot dog, dog, wiener,
       wienerwurst, weenie]